Aneurysms occur in blood vessels in locations where, due to age, disease or genetic predisposition, insufficient blood vessel strength or resiliency may cause the blood vessel wall to weaken and/or lose its shape as blood flows it, resulting in a ballooning or stretching of the blood vessel at the limited strength/resiliency location, thus forming an aneurysmal sac. Left untreated, the blood vessel wall may continue to expand to the point where the remaining strength of the blood vessel wall cannot hold and the blood vessel will fail at the aneurysm location, often with fatal result.
To prevent rupture of an aneurysm, a stent graft of a tubular construction may be introduced into the blood vessel and deployed and secured in a location within the blood vessel such that the stent graft spans the aneurysmal sac. The outer surface of the stent graft, at its opposed ends, abuts and seals against the interior wall of the blood vessel at a location where the blood vessel wall has not suffered a loss of strength or resiliency. The stent graft channels the blood flow through the hollow interior of the stent graft, thereby reducing, if not eliminating, any stress on the blood vessel wall at the aneurysmal sac location.
Stent grafts are typically configured by separately forming the graft and the stent(s), and then attaching the graft to stent(s). To attach a stent to a graft, the graft is typically inserted into, or pulled over, the stent, and the graft is sewn to the structural components of the stent. Alternatively, the stent may be formed on the graft such that the individual wires of the stent are threaded through specially provided projecting fabric loops on the surface of the graft, thereby creating attachment of the graft to the stent.
Attachment of the graft to the stent in these ways may result in an unneeded bulk. For example, the size of the stent graft, including the wire cage of the stent and the fabric of the graft, as well as the bulk of the connection mechanisms between them, limits the ultimate size of a stent graft that can be made that still fits within a catheter for smaller blood vessel diameter locations. Additionally, known mechanisms for attachment of the graft to the stent may provide potential sites for separation between the graft and stent. For example, during manufacture, handling or delivery of the stent graft, the attachment mechanisms may tear or fail, allowing the graft to partially or fully separate from the stent. Furthermore, attachment sites of the stent to graft may permit undesirable leakage of body fluids through the graft structure. For example, stents sutured to grafts may create interstices at the site of suture, increasing the grafts' porosity.